perf,ftrace: fuzzer triggers warning in trace_events_filter code

From: Vince Weaver <vincent.weaver@maine.edu>
To: linux-kernel@vger.kernel.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: perf,ftrace: fuzzer triggers warning in trace_events_filter code
Date: Fri, 12 Jun 2015 17:18:22 -0400 (EDT)	[thread overview]
Message-ID: <alpine.DEB.2.20.1506121713340.5186@vincent-weaver-1.umelst.maine.edu> (raw)

So I've modified my fuzzer to try to exercise the 
PERF_EVENT_IOC_SET_FILTER ioctl() and it is starting to turn up some 
warnings.

For example, this one:

[28509.873731] ------------[ cut here ]------------
[28509.879188] WARNING: CPU: 1 PID: 9572 at kernel/trace/trace_events_filter.c:1640 replace_preds+0x4f2/0x9b0()
[28509.890174] Modules linked in: fuse x86_pkg_temp_thermal intel_powerclamp snd_hda_codec_realtek intel_rapl iosf_mbi snd_hda_codec_hdmi snd_hda_codec_generic snd_hda_intel coretemp snd_hda_controller kvm_intel kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec snd_hda_core aesni_intel snd_hwdep tpm_tis ppdev i915 iTCO_wdt evdev iTCO_vendor_support snd_pcm aes_x86_64 snd_timer lrw snd tpm gf128mul soundcore glue_helper ablk_helper cryptd psmouse drm_kms_helper lpc_ich serio_raw pcspkr parport_pc mei_me mfd_core parport mei drm battery i2c_i801 video i2c_algo_bit wmi processor button sg sr_mod sd_mod cdrom ehci_pci ehci_hcd xhci_pci ahci xhci_hcd libahci libata e1000e crc32c_intel ptp fan scsi_mod usbcore pps_core usb_common thermal thermal_sys
[28509.967457] CPU: 1 PID: 9572 Comm: perf_fuzzer Tainted: G        W       4.1.0-rc7+ #155
[28509.976717] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS FBKT72AUS 01/26/2014
[28509.985188]  ffffffff81a1abb0 ffff8800ce757cb8 ffffffff816d7229 0000000000000000
[28509.993795]  0000000000000000 ffff8800ce757cf8 ffffffff81072eba 0000000000000160
[28510.002406]  ffff8800cda26208 ffff8800364e4a90 0000000000000000 ffff8800cda26200
[28510.010990] Call Trace:
[28510.014189]  [<ffffffff816d7229>] dump_stack+0x45/0x57
[28510.020242]  [<ffffffff81072eba>] warn_slowpath_common+0x8a/0xc0
[28510.027171]  [<ffffffff81072faa>] warn_slowpath_null+0x1a/0x20
[28510.033947]  [<ffffffff8114b3c2>] replace_preds+0x4f2/0x9b0
[28510.040401]  [<ffffffff8114c213>] ? ftrace_profile_set_filter+0x23/0x100
[28510.048083]  [<ffffffff8114b902>] create_filter+0x82/0xb0
[28510.054381]  [<ffffffff8114c244>] ftrace_profile_set_filter+0x54/0x100
[28510.061831]  [<ffffffff8119088b>] ? strndup_user+0x4b/0xc0
[28510.068170]  [<ffffffff811661c0>] perf_ioctl+0x170/0x4d0
[28510.074356]  [<ffffffff81202270>] do_vfs_ioctl+0x2e0/0x4e0
[28510.080681]  [<ffffffff81168305>] ? __perf_sw_event+0x65/0xa0
[28510.087299]  [<ffffffff8106312d>] ? __do_page_fault+0x2ad/0x460
[28510.094105]  [<ffffffff812024f1>] SyS_ioctl+0x81/0xa0
[28510.099983]  [<ffffffff816df172>] system_call_fastpath+0x16/0x7a
[28510.106857] ---[ end trace 2ea55cf8a8b076c3 ]---

This corresponds to
	/* Make sure the stack is empty */
                pred = __pop_pred_stack(&stack);
                if (WARN_ON(pred)) {
                        err = -EINVAL;
                        filter->root = NULL;
                        goto fail;
                }